1. Field of the Invention
The present invention relates to a magnetic head supporting device. More particularly, it relates to a magnetic head supporting device of a type wherein a flexible member is attached to a supporter at a portion near its free end; a loading projection is provided on the supporter to thereby transmit a loading force from the supporter to the flexible member, and a magnetic head having a slider attached with reading/writing elements is mounted on the lower surface of the flexible member.
2. Discussion of Background
In the magnetic head supporting device of this type, the following requirements have to be satisfied in order that the magnetic head can follow tracks formed in a surface of the magnetic disk with a predetermined small gap. Namely, a slider of the magnetic head holding reading/writing elements undergoes a pitching motion with respect to a first axis and a rolling motion with respect to a second axis which perpendicularly intersects the first axis to thereby remove uneven swinging motions. Such magnetic head supporting device is disclosed, for instance, in Japanese Examined Patent Publication No. 22827/1983 and Japanese Utility Model Publication No. 93868/1986.
FIG. 6 is a front view showing the relation between the conventional magnetic head supporting device and a magnetic disk and FIG. 7 is a plane view of the supporting device and the magnetic disk. In the figures, reference numeral 1 designates a magnetic disk and numeral 2 designates a magnetic head supporting device.
The magnetic disk 1 is driven in the direction of an arrow mark a by a driving unit (not shown). The magnetic head supporting device 2 is held by a positioning unit (not shown) so that it is driven linearly in the direction of an arrow mark b1 or b2, namely, in the radial direction along the diameter O.sub.1 of the rotating magnetic disk 1, and is positioned at a predetermined track so that writing operation to the magnetic disk 1 or reading operation from the disk 1 are carried out.
The magnetic head supporting device 2 comprises a supporter 22 made of a flexible thin elongated plate of a material such as stainless steel, one end of which is fixed to a rigid arm 21, which is in turn attached to the positioning unit, by means of fastening means 211, 212 such as screws. The other end in the longitudinal direction of the supporter 22 which constitutes a free end is attached with a flexible member 23. A magnetic head 24 is attached to the lower surface of the flexible member 23. The supporter 22 comprises a resilient spring portion 221 which constitutes a portion connected to the rigid arm 21. A rigid beam portion 222 is formed integrally with the resilient spring portion 221. The rigid beam portion 222 is provided at both sides with flanges 222a, 222b formed by bending both side portions of the rigid beam portion and this provides a loading force which pushes the magnetic head 24 toward the magnetic disk 1.
FIG. 8 is an enlarged front view showing an important part of the conventional magnetic head supporting device and FIG. 9 is a side view of the same. The flexible member 23 is made of a resilient metallic plate of a material such as stainless steel.
The flexible member 23 comprises a flexible flat plate portion, a pair of flexible outer frame portions 231, 232 formed integrally with both edges of the flat plate portion to extend substantially parallel to the axial line in the longitudinal direction of the supporter 22, a lateral frame 233 connecting both ends of the pair of flexible outer frame portions 231 and 232 at positions apart from the supporter 22, and a central tongue portion 234 which has an end connected to the intermediate portion of the lateral frame 233 and a free end extending toward the supporter, the free end extending between the pair of flexible outer frame portions 231, 232 and substantially parallel to the same. One end of the flexible member 23 which is opposite the lateral frame 233 is connected to the supporter 22 at a portion near its free end by using bonding means such as an adhesive. At substantially the central portion on the upper surface of the central tongue portion 234, a loading projection 235 having, for instance, a semi-spherical form is provided so that the loading projection 235 transmits a loading force from the free end of the supporter 22 to the central tongue portion 234. The loading projection 235 may be attached to the lower surface of the supporter 22 at a portion near the free end. The magnetic head 24 is attached to the lower surface of the central tongue portion 23 by means of, for instance, an adhesive agent.
The magnetic head 24 is provided with a slider 241 which constitutes a ceramic structure. A pair of rails 242, 243 are formed on a surface of the slider 241 with a length so as to face the magnetic disk 1. A pair of reading/writing elements 244, 245 such as thin film type magnetic head elements are attached to the end portions of the rails 242, 243. The surface of the reading/writing elements 244, 245 are covered by a protecting layer of a material such as a ceramic cover. Electrodes 246 and 247 or 248 and 249 each connected to a thin film type conductor coil are attached to the surface of the protecting layer. A pair of lead wires 4 of a linear material are bonded at one end thereof to either one of the reading/writing elements 244, 245, e.g. the electrodes 248, 249 of the reading/writing element 245. The lead wires 4 are bent in a loop and one end of the lead wires is extended toward the rigid beam portion 222 and the resilient spring portion 221 along the upper surface of the supporter 22.
In the above-mentioned conventional magnetic head supporting device, stable floating characteristics can be obtained at an area of flying height of more than 0.3 .mu.m. However, the conventional device has the following problems.
(a) In order to obtain magnetic recording of high density by determining a flying height to be less than 1/3 as the conventionally used flying height, i.e. less than 0.1 .mu.m to thereby reducing the spacing loss, it is necessary to reduce the surface area of the slider 241 opposing the magnetic disk so as to reduce a dynamic pressure for floating. In this case, since the flexible member 23 of the conventional supporting device is constituted by an resilient metallic plate of a material such as stainless steel, the elasticity of the flexible member 23 is too strong in comparison with a dynamic pressure for floating to the slider, with the result that it is difficult to balance the elasticity of the flexible member to the dynamic pressure, and stable control for the posture of the head can not be obtained.
(b) In order to balance the elasticity of the flexible member 23 and the dynamic pressure for floating, the flexible member inevitably has a complicated shape and a structure as disclosed in the above-mentioned publications. Since the flexible member is formed by the resilient metallic plate of stainless steel, it is difficult to form the flexible member into a complex structure. Especially, when the slider constituting the magnetic head is to be miniaturized to thereby accomplish a low flying height, it is necessary to reduce the size of the flexible member 23; this requires further difficult machining.
(c) Connecting and wiring operations are required for the lead wires 4 of a linear material which are to be connected to the electrodes 246 and 247 or 248 and 249 of either one of the reading/writing elements 244, 245. The wiring structure is complicated, and the wiring and assembling operations are troublesome.
(d) The function of the flexible member 23 is influenced by the elasticity of the lead wire 4 to thereby impair stable floating characteristics. If the elasticity of the flexible member 23 and the dynamic pressure for floating on the magnetic head 24 are made small so as to attain a low flying height, the elasticity of the lead wire 4 strongly influences the flexible member and the floating characteristics of the floating member is apt to change.
(e) It is necessary to form a large loop of the lead wire 4 in order to reduce the adverse effects of the elasticity of the lead wire. This results in possible contact of the looped lead wire 4 with the other elements.